A prior art of conventional bending machines is disclosed in the below-mentioned patent document 1 and this prior art will be described briefly as follows.
That is, the bending machine of the prior art performs bending with respect to a plate-like work by cooperating the upper bending mold and the lower bending mold and uses a pair of side frames that is opposed to each other in right and left sides and connected integrally as bases. The bending machine has an upper table provided on upper parts of the pair of side frames, a lower table provided on lower parts of the pair of side frames so as to be vertically opposed to the upper table and an NC device for controlling bending and the like.
Here, the upper table extends in the horizontal direction and an upper mold attachment part for attaching the upper bending mold thereto is provided on the bottom side of the upper table. The lower table extends in the horizontal direction and can move vertically with respect to the upper table, and a lower mold attachment part for attaching the lower bending mold thereto is provided on the top side of the upper table. The NC device controls various actuators, determines bending molds used for bending (the upper bending mold and the lower bending mold) and bending order (the order of bending when bending of one piece of work is performed plural times) on the basis of product information representing shape of the product and the like, and determines a layout mode of the bending molds in the horizontal direction.
A navigating tape for guiding the operator is stuck to a front face of the lower table or the upper table and the layout mode is represented on the navigating tape. Accordingly, the operator can attach the bending molds to the mold attachment parts (the upper mold attachment part and the lower mold attachment part) of the mold tables (the upper table and the lower table) according to the layout mode while being guided by the navigating tape.
On the other hand, another prior art of conventional bending machines is disclosed in the below-mentioned patent document 2. In this prior art, a back gauge for positioning the workpiece in the longitudinal direction can be moved in the longitudinal direction and in the horizontal direction. Generally, when bending position is determined, the back gauge is moved in the longitudinal direction. However, by transferring the back gauge in the horizontal direction, the back gauge is diverted to a device for positioning the molds in the horizontal direction.
Examples of the conventional arts include Japanese Patent Application Laid-Open No. 11-221630 (hereinafter referred to as “patent document 1”) and U.S. Pat. No. 5,969,973 (hereinafter referred to as “patent document 2”. Japanese Patent Application National Publication (Laid-Open) No. 9-509618 exists as a corresponding patent application. Priority Ser. No. 08/338,113, Nov. 9, 1994, United States, and Priority Ser. No. 08/386,369, Feb. 9, 1995, United States).
However, since the navigating tape in the patent document 1 is stuck to the front face of either of the tables, every time the layout mode changes, it is necessary to stick another navigating table representing the changed layout mode. For this reason, when plural types of bending is performed while changing the layout mode, a complicated operation (re-sticking of the navigating tape) is added, leading to a problem that operating time for a series of bending becomes longer, thereby to lower operating efficiency.
On the other hand, in the device in the patent document 2, even when positioning of the molds in the horizontal direction is possible, subsequent complicated positioning of the workpiece in the horizontal direction relies on the operator's experience. Accordingly, when the inexperienced operator performs bending, an error in bending is likely to occur.
Especially, when a window (aperture) is formed at an inner side of the workpiece so as to be surrounded and a small protrusion in the window is bent upwards (cut-raising), the position of the workpiece in the horizontal direction with respect to the molds needs to be determined accurately. In the event that this positioning is inaccurate, although the small protrusion in the window (aperture) needs to be bent, the part surrounding the window (aperture) is also bent, leading to an error in bending.
To solve the above-mentioned problem, a first object of the present invention is provide a bending machine capable of positioning the workpiece and the molds in the horizontal direction accurately even by the inexperienced operator.
A second object of the present invention is to provide a bending machine capable of avoiding interference of a work positioning means with the workpiece.